The woman who shot and killed her two grandchildren and then herself is another profound tragedy, but it would not have been prevented by the gun control measures proposed as a result of the Sandy Hook School massacre.
Common amongst all of the recent mass shootings has been a mental illness. Due to budgetary problems, people ill enough to require institutionalization are now living in the community. Many living amongst us may not be fit to do so.
Addressing mental health first could yield immediate results. It could be implemented with no delays due to protracted defenses of the Second Amendment.
Attacks on the Second Amendment can continue and be very divisive and counter-productive. There is little chance that amendment's supporters will relent. Years from now we will still have no effective legislation that will address the problem of mass shootings by the mentally ill. If history is a predictor of future events, there will be more shootings by mentally ill people that could have been prevented.
Concentrating on guns rather than mental illness is like fixing a leaky dam by hand-bailing the pond dry rather than plugging the leak in the wall. It may eventually stop the leak, but it will take a long time, and a lot of good water will be lost.